Cast
Larry Kent
Lt. 'Mac' McGregor
William Collier Sr.
Mugs O'Flaherty (uncredited)
Francis Ford
Eric - Captain of Trawler (uncredited)
Maurice Murphy
Merkel (uncredited)
Edward Peil Jr.
Naval Reservist (uncredited)
Warren Hymer
'Lug' Kaufman
Walter McGrail
Chief Joe Cobb
Henry Victor
Baron Ernst von Steuben (U-boat commander)
Nat Pendleton
'Butch' Wagner (uncredited)
Harry Strang
Gunner and drill sergeant (uncredited)
George O'Brien
Cmdr. Robert 'Bob' Kingsley
Marion Lessing
Anna Marie Von Steuben
Mona Maris
Fraulein Lolita
Jack Murphy
Naval Reservist (uncredited)
Joseph Depew
Naval Reservist (uncredited)
Hans Fuerberg
Fritz Kampf (Second Officer of U-172) (uncredited)
George Harris
Naval Reservist/Swimmer and Diver (uncredited)
Harry Tenbrook
Winkler (uncredited)
John Loder
Franz Shiller
Ferdinand Schumann-Heink
Adolph Brucker (uncredited)
Walter C. Kelly
Chief Mike 'Guns' Costello
Steve Pendleton
Ens. Richard 'Dick' Cabot (as Gaylord Pendleton)